Heat Exchanger Fouling Performance & Pressure Drop Analyzer
Calculate actual heat transfer rate and actual pressure drop using clean heat transfer rate, clean pressure drop, fouling factor, and operating constraint.
Enter the known values and review the calculated result
Input parameters
Use consistent values and select the intended engineering units.
Operating constraints
Thermal performance (clean conditions)
Hydraulic performance (clean conditions)
Fouling characteristics
Fluid properties
Flow and geometry
Results
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Method, application and limitations
Review the calculation method, intended application and engineering assumptions before using the result in a design decision.
Formula and calculation method
Actual heat transfer rate formula and actual pressure drop formula:
For constant flow:
Q = Qclean / (1 + f)
ΔP = ΔPclean · (1 + 2.5 · f)
For constant pressure:
ΔP = ΔPclean
Qflow,actual = Qflow / √(1 + 2.5 · f)
Q = (Qclean / (1 + f)) · (Qflow,actual / Qflow)
where:
- Q — actual heat transfer rate
- ΔP — actual pressure drop
- Qclean — clean heat transfer rate
- ΔPclean — clean pressure drop
- f — fouling factor [-]
- Qflow — volumetric flow rate
- Qflow,actual — actual volumetric flow rate
When to use this calculator
When to use this calculator:
- To estimate actual heat transfer rate when fouling reduces clean thermal performance.
- To calculate actual pressure drop when fouling increases hydraulic resistance under constant flow operation.
- To evaluate flow reduction when the exchanger operates under constant pressure drop.
- To compare thermal performance loss against hydraulic penalty caused by fouling.
- To check whether fouling causes operation to move into limit, warning, unsafe, or invalid result conditions.
How to interpret the result
Actual heat transfer rate is defined as the remaining heat transfer rate after fouling impact is applied to the clean heat transfer rate.
Actual pressure drop is defined as the clean pressure drop modified by the hydraulic penalty in constant flow operation, or kept equal to the clean pressure drop in constant pressure operation.
Actual heat transfer rate depends on clean heat transfer rate, fouling factor, and actual flow reduction. Increasing clean heat transfer rate increases actual heat transfer rate. Increasing fouling factor decreases actual heat transfer rate.
Actual pressure drop depends on clean pressure drop and fouling factor in constant flow operation. Increasing clean pressure drop increases actual pressure drop. Increasing fouling factor increases actual pressure drop under constant flow operation.
- Safe — efficiency loss is ≤ 15%, hydraulic penalty ratio is ≤ 1.4, efficiency loss is ≤ 25%, hydraulic penalty ratio is ≤ 1.8, operability index is ≥ 0.6, efficiency loss is ≤ 40%, hydraulic penalty ratio is ≤ 2.5, and operability index is ≥ 0.4.
- Limit — efficiency loss is > 15% or hydraulic penalty ratio is > 1.4, while warning and unsafe conditions are not reached.
- Warning — efficiency loss is > 25%, hydraulic penalty ratio is > 1.8, or operability index is < 0.6, while unsafe conditions are not reached.
- Unsafe — efficiency loss is > 40%, hydraulic penalty ratio is > 2.5, or operability index is < 0.4.
- Invalid — input or computed values violate model limits, including Reynolds number above 1e8, actual-to-clean heat transfer ratio below 0.05, non-positive actual heat transfer rate, non-positive actual pressure drop, or non-positive actual flow rate.
The result is used to evaluate whether fouling reduces thermal output, increases hydraulic resistance, or causes the exchanger to operate outside accepted calculation limits.
Calculation example
Example:
A user checks a fouled heat exchanger operating at constant flow to estimate the reduced heat transfer rate and increased pressure drop.
- Constraint type — Flow vs pressure control: Constant flow
- Qclean — Clean heat transfer rate: 100 kW
- ΔPclean — Clean pressure drop: 50 kPa
- f — Fouling factor [-]: 0.5
- μ — Dynamic viscosity: 0.001 Pa·s
- ρ — Fluid density: 1000 kg/m³
- Qflow — Volumetric flow rate: 0.01 m³/s
- D — Hydraulic diameter: 0.1 m
Q = 66.7 kW and ΔP = 112.5 kPa.
Assumptions and limitations
- The operating constraint is either constant flow or constant pressure.
- Fouling impact is calculated as 1 + fouling factor.
- Hydraulic penalty is calculated as 1 + 2.5 times fouling factor.
- Under constant flow operation, actual flow rate is equal to the entered volumetric flow rate.
- Under constant pressure operation, actual pressure drop is equal to clean pressure drop.
- Under constant pressure operation, actual flow rate is reduced by the square root of the hydraulic penalty.